Frontier quality,
cheap-model prices.

Dolphin's answer check 100/100 · $0.000003

Canberra

The answer is correct and follows the one-word requirement.

Premium answer check 100/100 · $0.0024

Canberra

The answer correctly gives Canberra in the requested one-word format.

Dolphin's answer check 100/100 · $0.000002

212

The answer is correct and follows the instruction to provide just the number.

Premium answer check 100/100 · $0.0024

212

The answer is correct and follows the request to provide only the number.

Dolphin's answer check 96/100 · $0.000016

x402 is an open payment protocol that uses the long-reserved HTTP 402 “Payment Required” status code to let clients—including AI agents—pay programmatically for APIs and web resources. It is designed for machine-to-machine, pay-per-use access, typically settling stablecoin payments onchain without traditional accounts or subscriptions.

It answers in two sentences and accurately explains HTTP 402, programmatic pay-per-use access, AI agents, and stablecoin settlement, with only a minor potentially unsupported detail about avoiding traditional accounts or subscriptions.

Premium answer check 85/100 · $0.0080

x402 is an open payment protocol introduced by Coinbase in 2025 that revives the HTTP 402 "Payment Required" status code so servers can request payment directly within a standard web request. Clients, including AI agents, can then pay instantly, typically in stablecoins like USDC, enabling pay-per-use access to APIs and content without accounts, API keys, or subscriptions.

It correctly explains the HTTP 402 payment flow and typical stablecoin payments by clients such as AI agents, but adds unsupported or overly absolute claims about its origin, instant settlement, and eliminating accounts, keys, or subscriptions.

Dolphin's answer check 100/100 · $0.000017

Plants use sunlight, water, and air to make their own food. Their leaves catch sunlight like solar panels. Water comes up from roots, and carbon dioxide enters through tiny holes. They turn these into sugar for energy and release oxygen we breathe.

The explanation is accurate, age-appropriate, and under 60 words, covering sunlight, water, carbon dioxide, sugar, and oxygen.

Premium answer check 100/100 · $0.0049

Plants make their own food using sunlight! Their leaves soak up sunshine, drink water through their roots, and breathe in carbon dioxide (a gas in the air). Using the sun's energy, they mix these together to make sugar, their food. As a bonus, they release oxygen, the air we breathe. Thanks, plants!

The answer is accurate, simple, and under 60 words, explaining that plants use sunlight, water, and carbon dioxide to make sugar and release oxygen.

Dolphin's answer check 100/100 · $0.000012

Proof-of-work secures a blockchain through computational effort: miners spend energy solving puzzles to validate blocks and earn rewards. Proof-of-stake replaces that with economic collateral: validators lock up tokens as stake and are chosen to validate blocks, earning rewards but risking penalties. The main difference is that PoW relies on energy expenditure, while PoS relies on locked capital.

The answer accurately contrasts PoW’s computational work and energy use with PoS’s staked tokens, and it is under 100 words.

Premium answer check 100/100 · $0.0075

**Proof-of-work (PoW)** secures a blockchain by having miners compete to solve computationally hard puzzles. The first to solve one adds the next block and earns a reward. This requires massive energy and specialized hardware.

**Proof-of-stake (PoS)** selects validators based on the amount of cryptocurrency they lock up ("stake") as collateral. Validators propose and confirm blocks, and dishonest behavior can cost them their stake.

**Main difference:** PoW relies on computational effort and energy expenditure for security, while PoS relies on economic stake, making it far more energy-efficient.

The answer accurately contrasts PoW’s computational work and energy use with PoS’s reliance on staked cryptocurrency, and it is under 100 words.

Dolphin's answer check 100/100 · $0.000002

36

The answer is correct and follows the instruction to provide just the number.

Premium answer check 100/100 · $0.0024

36

The answer is correct and follows the request to provide only the number.

Dolphin's answer check 100/100 · $0.000004

$12

The answer is correct and follows the instruction to show the answer only.

Premium answer check 100/100 · $0.0025

$12

The answer is correct and follows the instruction to provide the answer only.

Dolphin's answer check 100/100 · $0.000008

After 3 years:

\[
1000(1.05)^3 = 1000 \times 1.157625 = 1157.625
\]

Rounded to the cent:

\[
\boxed{\$1,157.63}
\]

The calculation correctly applies annual compounding for three years and rounds $1,157.625 to $1,157.63.

Premium answer check 100/100 · $0.0050

**$1,157.63**

A = 1,000 × (1.05)³ = 1,000 × 1.157625 = 1,157.625, which rounds to $1,157.63.

The answer correctly applies annual compounding for three years and rounds $1,157.625 to $1,157.63.

Dolphin's answer check 85/100 · $0.000008

The prime numbers between 50 and 70 are:

**53, 59, 61, 67**

It lists all the correct primes, but adds introductory text despite the request for the numbers and nothing else.

Premium answer check 90/100 · $0.0036

The prime numbers between 50 and 70 are **53, 59, 61, and 67**.

The answer lists all and only the correct primes, but includes extra wording despite the requested list-only format.

Dolphin's answer check 100/100 · $0.000004

There are **12,600 seconds** in 3.5 hours.

The answer correctly states that 3.5 hours equals 12,600 seconds.

Premium answer check 100/100 · $0.0036

There are **12,600 seconds** in 3.5 hours (3.5 × 60 × 60 = 12,600).

The answer correctly converts 3.5 hours to 12,600 seconds and shows the calculation.

Dolphin's answer check 100/100 · $0.000018

```python
def fizzbuzz(n):
    result = []
    for i in range(1, n + 1):
        if i % 15 == 0:
            result.append("FizzBuzz")
        elif i % 3 == 0:
            result.append("Fizz")
        elif i % 5 == 0:
            result.append("Buzz")
        else:
            result.append(str(i))
    return result
```

The function correctly returns the required strings for every integer from 1 through n, including all three FizzBuzz cases.

Premium answer check 100/100 · $0.01

```python
def fizzbuzz(n):
    """Return a list of FizzBuzz strings for the numbers 1 through n."""
    result = []
    for i in range(1, n + 1):
        if i % 15 == 0:
            result.append("FizzBuzz")
        elif i % 3 == 0:
            result.append("Fizz")
        elif i % 5 == 0:
            result.append("Buzz")
        else:
            result.append(str(i))
    return result
```

Example:

```python
>>> fizzbuzz(15)
['1', '2', 'Fizz', '4', 'Buzz', 'Fizz', '7', '8', 'Fizz', 'Buzz',
 '11', 'Fizz', '13', '14', 'FizzBuzz']
```

Notes:
- Multiples of both 3 and 5 are checked first (`i % 15 == 0`). Otherwise those numbers would match the "Fizz" branch before reaching "FizzBuzz".
- If `n` is less than 1, the function returns an empty list.

The function correctly returns the required strings for 1 through n, handles multiples of both 3 and 5 before individual cases, and the example and note are accurate.

Dolphin's answer check 95/100 · $0.000017

```javascript
function reverseWords(sentence) {
  const trimmed = sentence.trim();
  if (trimmed === '') return '';
  return trimmed.split(/\s+/).reverse().join(' ');
}
```

The function correctly reverses words and handles extra whitespace, but the Markdown code fence does not strictly satisfy the request for code only.

Premium answer check 98/100 · $0.0035

```javascript
function reverseWords(sentence) {
  return sentence.trim().split(/\s+/).reverse().join(' ');
}
```

The JavaScript correctly reverses the words and contains no explanatory text, though the Markdown fences are a minor departure from code-only formatting.

Dolphin's answer check 100/100 · $0.000024

```sql
SELECT customer_id, SUM(amount) AS total_amount
FROM orders
GROUP BY customer_id
ORDER BY total_amount DESC
LIMIT 5;
```

This groups orders by `customer_id`, sums each customer’s order amounts, and returns the top 5 by total amount.

For SQL Server, replace `LIMIT 5` with `SELECT TOP 5 ...`. If you need deterministic handling of ties, use a window function such as `DENSE_RANK()`.

The query correctly groups by customer, sums order amounts, sorts totals descending, and limits the result to five customers.

Premium answer check 100/100 · $0.01

```sql
SELECT customer_id,
       SUM(amount) AS total_amount
FROM orders
GROUP BY customer_id
ORDER BY total_amount DESC
LIMIT 5;
```

**Notes:**
- `LIMIT 5` works in PostgreSQL, MySQL, SQLite, and similar databases.
- In **SQL Server**, use `SELECT TOP 5 customer_id, SUM(amount) AS total_amount ...` instead of `LIMIT`.
- In **Oracle 12c+** or standard SQL, use `FETCH FIRST 5 ROWS ONLY` in place of `LIMIT 5`.
- If you want customers tied at 5th place included, use a window function:

```sql
SELECT customer_id, total_amount
FROM (
    SELECT customer_id,
           SUM(amount) AS total_amount,
           RANK() OVER (ORDER BY SUM(amount) DESC) AS rnk
    FROM orders
    GROUP BY customer_id
) t
WHERE rnk <= 5;
```

The query correctly groups orders by customer, sums amounts, sorts totals in descending order, and returns the top five customers.

Dolphin's answer check 100/100 · $0.000010

The bug is the extra `- 1`: it computes the mean and then subtracts 1.

Fix:

```python
def avg(xs):
    return sum(xs) / len(xs)
```

(If empty lists are possible, handle `len(xs) == 0` separately.)

Correctly identifies the unintended subtraction and removes it; the optional empty-list note is accurate and concise.

Premium answer check 100/100 · $0.01

**Bug:** Division binds tighter than subtraction, so this computes `(sum(xs) / len(xs)) - 1`, which is the average minus 1.

**Fix:** Remove the `- 1`:

```python
def avg(xs):
    return sum(xs) / len(xs)
```

If you actually meant to divide by `n - 1`, add parentheses: `sum(xs) / (len(xs) - 1)`.

Note that an empty list will raise `ZeroDivisionError`, so guard against it if needed.

Correctly explains the precedence and average-minus-one result, gives the expected fix, and adds a valid note about empty input.

Dolphin's answer check 100/100 · $0.000014

```regex
^[0-9]{5}(-[0-9]{4})?$
```

This matches `12345` or `12345-6789`. Use `\d{5}(-\d{4})?` if you don’t need full-string anchors.

The anchored expression matches exactly five digits, optionally followed by a hyphen and four digits, as requested.

Premium answer check 95/100 · $0.0090

```regex
^\d{5}(-\d{4})?$
```

- `^` and `$` anchor the match to the whole string.
- `\d{5}` matches exactly 5 digits.
- `(-\d{4})?` optionally matches a dash followed by exactly 4 digits.

**Matches:** `12345`, `12345-6789`
**Rejects:** `1234`, `123456`, `12345-678`, `12345 6789`

If your regex engine's `\d` can match non-ASCII digits (as in Python 3 or .NET), use `[0-9]` instead:

```regex
^[0-9]{5}(-[0-9]{4})?$
```

To find ZIP codes inside longer text, replace the anchors with word boundaries: `\b\d{5}(-\d{4})?\b`.

The anchored regex correctly matches the requested ZIP code format, though the word-boundary suggestion can match a five-digit prefix of a malformed ZIP+4 value.

Dolphin's answer check 100/100 · $0.000014

1. Manila roasted. Freshly poured, always.  
2. Small-batch Manila coffee, roasted for you.  
3. Local beans. Bold Manila mornings.

It provides exactly three relevant taglines, each with fewer than eight words.

Premium answer check 100/100 · $0.0087

1. Small batch. Big Manila heart.
2. Roasted in Manila, brewed for every barkada.
3. From Philippine highlands to your morning cup.

It provides exactly three relevant taglines, each under eight words.

Dolphin's answer check 100/100 · $0.000018

Subject: Re: Meeting Invitation

Thank you for the invitation to meet; unfortunately, I have a schedule clash at the proposed time and won’t be able to attend. Would either Tuesday at 10:00 a.m. or Thursday at 2:00 p.m. work as alternatives? I appreciate your understanding and look forward to finding a time that suits everyone.

The email is polite, declines because of a schedule clash, and offers two alternative times in exactly three sentences.

Premium answer check 100/100 · $0.0079

Subject: Rescheduling Our Meeting

Hi [Name],

Thank you for the invitation, but unfortunately I have a prior commitment at that time and won't be able to attend. Would either Tuesday at 10:00 AM or Thursday at 2:00 PM work for you instead? I appreciate your flexibility and look forward to connecting.

Best regards,
[Your Name]

The email is polite, declines because of a prior commitment, and offers two alternative times in exactly three sentences.

Dolphin's answer check 90/100 · $0.000014

We combine AI approaches to turn scalable value creation into practice.

The answer is plain and under 30 words, and it preserves the core meaning, though “turn scalable value creation into practice” is slightly awkward.

Premium answer check 95/100 · $0.0030

We use different AI tools together to help the business grow and make money efficiently.

The rewrite is plain English, under 30 words, and preserves the core idea of combining AI approaches to create business value.

Dolphin's answer check 100/100 · $0.000007

The city council voted 7-2 Tuesday to approve a state-funded bike lane on Main Street, to be built next spring.

The sentence accurately captures the 7–2 approval, the Main Street bike lane, its construction next spring, and state grant funding.

Premium answer check 100/100 · $0.0038

The city council voted 7-2 on Tuesday to approve a state-funded Main Street bike lane, to be built next spring.

The answer accurately captures the 7-2 approval, Main Street bike lane, construction next spring, and state grant funding in one sentence.

Dolphin's answer check 100/100 · $0.000013

Monsoon rains arrive—
grey clouds spill their heavy tears;
earth drinks deep and sings.

The poem evokes the monsoon season and follows a clear 5-7-5 syllable pattern across three lines.

Premium answer check 100/100 · $0.0068

**Monsoon**

Dark clouds swallow noon,
rain drums on the tin rooftops,
frogs sing to the flood.

The answer is a vivid three-line monsoon poem with a 5-7-5 syllable pattern.

Dolphin's answer check 100/100 · $0.000003

Carol.

The answer correctly identifies Carol as the shortest.

Premium answer check 100/100 · $0.0040

**Carol** is the shortest. Since Alice is taller than Bob and Bob is taller than Carol, the order from tallest to shortest is Alice, Bob, Carol.

The answer correctly identifies Carol as the shortest and supports it with the stated height ordering.

Dolphin's answer check 100/100 · $0.000005

The ball costs **$0.05** (5 cents).

The answer correctly states that the ball costs $0.05 (5 cents).

Premium answer check 100/100 · $0.0072

**The ball costs $0.05 (5 cents).**

If the ball costs *x*, the bat costs *x* + $1.00, so:

- *x* + (*x* + $1.00) = $1.10
- 2*x* = $0.10
- *x* = $0.05

**Check:** The ball is $0.05 and the bat is $1.05, which totals $1.10, and the bat costs exactly $1.00 more.

The intuitive answer of 10 cents is wrong. With a 10-cent ball the bat would cost $1.10, making the total $1.20.

The answer correctly derives that the ball costs $0.05 and verifies the total and price difference.

Dolphin's answer check 100/100 · $0.000005

It ends at **11:05**.

The answer correctly states that 85 minutes after 9:40 is 11:05.

Premium answer check 100/100 · $0.0039

The meeting ends at **11:05**. Adding 85 minutes (1 hour 25 minutes) to 9:40 gives 11:05.

The answer correctly calculates the end time as 11:05 and clearly explains the 85-minute addition.

Dolphin's answer check 100/100 · $0.000004

Carrot is the odd one out because it is a vegetable, while apple, banana, and mango are fruits.

The answer correctly identifies carrot as the vegetable and explains that the other three are fruits.

Premium answer check 100/100 · $0.0040

**Carrot** is the odd one out because it's a root vegetable, while apple, banana, and mango are all fruits.

The answer correctly identifies carrot as the odd one out and explains that the others are fruits.

Dolphin's answer check 100/100 · $0.000012

1. Fill the 5L jug.  
2. Pour into the 3L jug, leaving 2L in the 5L jug.  
3. Empty the 3L jug, then pour the 2L into it.  
4. Fill the 5L jug again, then pour into the 3L jug until full (takes 1L).  
5. Exactly 4L remain in the 5L jug.

The steps are valid and end with exactly 4 litres in the 5-litre jug.

Premium answer check 100/100 · $0.0077

1. Fill the 5L jug.
2. Pour from it into the 3L jug until full, leaving 2L in the 5L jug.
3. Empty the 3L jug.
4. Pour the 2L into the 3L jug.
5. Refill the 5L jug.
6. Top up the 3L jug from the 5L jug. It takes only 1L, leaving **exactly 4L** in the 5L jug.

The sequence is valid and ends with exactly 4 litres in the 5-litre jug.

Dolphin's answer check 100/100 · $0.000016

I don’t know and can’t verify OpenServ’s exact revenue for March 2026. It doesn’t appear to be publicly disclosed, and I don’t have a reliable source for that figure. If you have a filing, dashboard, or announcement, I can help interpret it.

It appropriately says the exact revenue is unknown and unverifiable rather than inventing a figure.

Premium answer check 95/100 · $0.0083

I don't know OpenServ's exact revenue for March 2026, and I can't verify it. I have no reliable data for that figure. Monthly revenue for a company like OpenServ is also not usually made public, especially if it's privately held.

To find it, you could check:
- **Official company announcements**, such as their blog, press releases, or investor updates
- **Their official social media channels**
- **On-chain data or token dashboards**, if OpenServ has an associated token or protocol revenue that's tracked publicly (e.g., DefiLlama, Token Terminal)
- **Financial news coverage** or **direct contact** with the company

It clearly says the exact figure is unknown and unverifiable without inventing a number, though the extra claims and suggested sources are somewhat speculative.

Dolphin's answer check 100/100 · $0.000011

The 2030 FIFA World Cup has not been played yet, so there is no winner. It is scheduled for 2030, with Spain, Portugal, and Morocco as main hosts and centenary matches planned in Uruguay, Argentina, and Paraguay.

It correctly says the 2030 World Cup has not been played and has no winner, and its additional hosting details are accurate.

Premium answer check 100/100 · $0.0079

I don't know who won the 2030 FIFA World Cup. As of my latest information, the tournament hasn't taken place yet. It's scheduled for 2030, co-hosted mainly by **Spain, Portugal, and Morocco**, with three opening matches in **Uruguay, Argentina, and Paraguay** to mark the competition's centenary.

For the result, check an up-to-date source like FIFA's official website or a current news outlet.

Correctly states that the 2030 tournament has not yet taken place and does not invent a winner.

Dolphin's answer check 100/100 · $0.000024

I can’t reliably summarise *The Glass Orchard of Mars* by Elena Varga (2019) because I don’t have verified information about that book, and I can’t confirm that title/author/publication details exist as described. To avoid inventing a plot, I won’t guess.

If you can provide an ISBN, publisher, back-cover text, or a link, I can summarise it accurately.

It explicitly says the book cannot be verified and avoids inventing a plot, while offering a useful way to proceed.

Premium answer check 100/100 · $0.0063

I can't find any record of a book called *The Glass Orchard of Mars* by Elena Varga (2019), so I can't summarise it without inventing details. It may be a small-press or self-published release, a translated title, or the title or author name may be slightly different.

If you can share more details, such as the publisher, ISBN, or a blurb, I can help with what you have. If you paste a description or excerpt, I can summarise that text directly.

It appropriately says it cannot verify the book, avoids inventing a plot, and offers useful next steps.

Dolphin's answer check 100/100 · $0.000005

{"name":"Maria","age":30}

The answer is valid JSON with the requested name and age and no extra text.

Premium answer check 100/100 · $0.0028

{"name": "Maria", "age": 30}

The answer is valid JSON with the requested name and age and no extra text.

Dolphin's answer check 100/100 · $0.000006

1. Jupiter
2. Saturn
3. Neptune

The answer is a numbered list of exactly three planets larger than Earth, with no explanations.

Premium answer check 100/100 · $0.0029

1. Jupiter
2. Saturn
3. Uranus

The answer lists exactly three permitted planets in the requested numbered-list format and includes no explanations.

Dolphin's answer check 100/100 · $0.000095

121932631112635269

The answer is exactly correct and follows the request for just the number.

Premium answer check 100/100 · $0.01

121932631112635269

The answer gives the exact product and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000014

400

The answer is correct and follows the request to provide only the number.

Premium answer check 100/100 · $0.0041

400

The answer is correct and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000021

115

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0063

115

The answer is exactly correct.

Dolphin's answer check 100/100 · $0.000020

229

The answer correctly gives the 50th prime number and follows the instruction to provide just the number.

Premium answer check 100/100 · $0.0054

229

The answer correctly gives the 50th prime number as 229.

Dolphin's answer check 100/100 · $0.000004

249

The answer is correct: 1000! has 249 trailing zeros.

Premium answer check 100/100 · $0.0024

249

The answer is correct and follows the requested format.

Dolphin's answer check 100/100 · $0.000007

34650

The answer is correct and gives only the requested number.

Premium answer check 100/100 · $0.0034

34650

The answer is correct and follows the request to provide just the number.

Dolphin's answer check 100/100 · $0.000009

177

The answer is correct and follows the request to provide just the number.

Premium answer check 100/100 · $0.0043

177

The answer is correct and follows the request to provide just the number.

Dolphin's answer check 100/100 · $0.000007

\[
1-\left(\frac{5}{6}\right)^4
=1-\frac{625}{1296}
=\boxed{\frac{671}{1296}}
\]

The answer correctly uses the complement probability and gives the exact fraction \(671/1296\).

Premium answer check 100/100 · $0.0061

The probability is **671/1296** (about 0.518).

It's easiest to find the probability of the opposite event and subtract from 1:

- The chance of not rolling a six on one roll is 5/6.
- The chance of no six in four rolls is (5/6)⁴ = 625/1296.
- So the chance of at least one six is 1 − 625/1296 = **671/1296**.

The answer correctly computes the exact probability as 671/1296 and explains the complement method accurately.

Dolphin's answer check 100/100 · $0.000003

231

The answer is correct and follows the instruction to provide just the number.

Premium answer check 100/100 · $0.0027

231

The answer is correct and follows the request to give just the number.

Dolphin's answer check 100/100 · $0.000004

40

The answer is correct: the total distance is 120 km and the total time is 3 hours, giving an average speed of 40 km/h.

Premium answer check 90/100 · $0.0031

Time: 2h + 1h = 3h; distance 120 km.

40

The average speed is correctly given as 40 km/h, but the explanation violates the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000006

6857

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0024

6857

The answer is correct and follows the request to provide just the number.

Dolphin's answer check 100/100 · $0.000006

32570

The answer correctly converts 0x7F3A to 32570 and follows the requested format.

Premium answer check 100/100 · $0.0037

32570

The answer correctly converts 0x7F3A to decimal and follows the requested format.

Dolphin's answer check 100/100 · $0.000007

0.142857142857

The answer correctly gives 1/7 to exactly 12 decimal places.

Premium answer check 100/100 · $0.0053

**1/7 ≈ 0.142857142857**

The repeating block is 142857, and the 13th digit is 1, so rounding leaves the 12th digit unchanged.

The answer gives 1/7 rounded to exactly 12 decimal places correctly and accurately explains why rounding does not change the final digit.

Dolphin's answer check 100/100 · $0.0002

The monthly rate is \(0.06/12=0.005\), and there are \(10 \times 12=120\) months.

\[
A=5000(1.005)^{120}\approx 9096.98367
\]

To the cent, the final balance is:

\[
\boxed{\$9,096.98}
\]

The answer correctly applies monthly compounding for 120 months and rounds the final balance to $9,096.98.

Premium answer check 100/100 · $0.02

The final balance is **$9,096.98**.

This uses the compound interest formula A = P(1 + r/n)^(nt):

- Principal (P) = $5,000
- Annual rate (r) = 0.06
- Compounding periods per year (n) = 12
- Years (t) = 10

A = 5000 × (1 + 0.06/12)^(12×10)
A = 5000 × (1.005)^120
A ≈ 5000 × 1.8193967
A ≈ **$9,096.98**

That is about $4,096.98 in interest.

The compound-interest formula is applied correctly, and the final balance is $9,096.98 to the cent.

Dolphin's answer check 100/100 · $0.000011

1548008755920

The answer gives the correct 60th Fibonacci number.

Premium answer check 100/100 · $0.0036

1548008755920

The answer is correct and follows the requested format.

Dolphin's answer check 100/100 · $0.000003

31622400

The answer gives the correct number of seconds in a 366-day year and follows the requested format.

Premium answer check 100/100 · $0.0028

31622400

The answer is correct and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000008

7.5

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0036

7.5

The answer is correct and follows the instruction to give only the number of degrees.

Dolphin's answer check 100/100 · $0.000005

10

The answer is correct and follows the request to give just the number.

Premium answer check 100/100 · $0.0033

10

The answer is correct: the son is 10 years old.

Dolphin's answer check 100/100 · $0.000004

1

The answer is correct: Alice is the one sister shared by her three brothers.

Premium answer check 100/100 · $0.0025

1

The answer is correct: Alice is the other sister shared by her three brothers.

Dolphin's answer check 100/100 · $0.0001

No. Under the usual assumption that the ignorant host randomly chooses one of the two unopened doors and happens to reveal a goat, switching does **not** improve your chances.

After observing door 3 opened with a goat:

- If the car is behind door 1: probability of that observation = \( \frac13 \cdot \frac12 = \frac16 \)
- If the car is behind door 2: probability of that observation = \( \frac13 \cdot \frac12 = \frac16 \)
- If the car is behind door 3: probability = \(0\), since a goat was shown

So conditional on the host having randomly revealed a goat behind door 3:

\[
P(\text{car behind door 1})=\frac{1/6}{1/6+1/6}=\frac12
\]

\[
P(\text{car behind door 2})=\frac12
\]

Therefore, **the probability of winning if you switch is \(\boxed{\frac12}\)**. Switching is not better than staying; both have probability \(1/2\). This differs from the standard Monty Hall problem, where the host knowingly opens a goat door, making switching win with probability \(2/3\).

The answer correctly conditions on the host randomly opening door 3 and finding a goat, yielding a 1/2 chance of winning by switching and no advantage over staying.

Premium answer check 100/100 · $0.02

**No, switching does not improve your chances.** If you switch, your probability of winning is **1/2**, the same as staying.

**Why:** Because the host doesn't know where the car is, his revealing a goat is luck rather than deliberate. That changes the math from the classic version.

Each door starts with a 1/3 chance of hiding the car. The host randomly opens door 3:

| Car location | Prior | Chance door 3 shows a goat | Joint probability |
|---|---|---|---|
| Door 1 | 1/3 | 1 | 1/3 |
| Door 2 | 1/3 | 1 | 1/3 |
| Door 3 | 1/3 | 0 | 0 |

Given that a goat appeared, only the first two rows remain, and they are equally likely:

- P(car behind door 1 | goat) = (1/3) / (2/3) = **1/2**
- P(car behind door 2 | goat) = (1/3) / (2/3) = **1/2**

In the classic Monty Hall problem, the host *knows* where the car is and always avoids it. That guaranteed goat reveal is what pushes switching up to 2/3. With an ignorant host, the random reveal gives no extra information favoring door 2.

The answer correctly concludes that switching offers no advantage and gives a 1/2 chance of winning, with valid conditional-probability reasoning.

Dolphin's answer check 100/100 · $0.000003

Second

The answer is correct and follows the one-word requirement.

Premium answer check 100/100 · $0.0024

Second

The answer is correct and follows the one-word requirement.

Dolphin's answer check 100/100 · $0.000004

5

The answer is correct: 100 machines make 100 widgets in 5 minutes.

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5

The answer is correct and follows the instruction to give just the number.

Dolphin's answer check 100/100 · $0.000005

A kilogram of feathers is heavier, since 1 kg equals about 2.2 pounds.

Correctly identifies the kilogram of feathers as heavier and gives the accurate conversion in one sentence.

Premium answer check 100/100 · $0.0039

A kilogram of feathers is heavier, since 1 kg is about 2.2 pounds.

Correctly identifies the kilogram of feathers as heavier and explains that 1 kg is about 2.2 pounds.

Dolphin's answer check 100/100 · $0.000017

A is a **knight**, and B is a **knave**.

- If A is a knight, A’s statement that “B is a knave” is true, so B is a knave.
- B’s statement “A and I are both knights” is then false, which is consistent because B is a knave.

The answer correctly identifies A as a knight and B as a knave and verifies that both statements fit their roles.

Premium answer check 100/100 · $0.0080

**A is a knight and B is a knave.**

- **Suppose B is a knight.** Then B's statement is true, so A is also a knight. But A says B is a knave, which would be a lie from a knight. Contradiction, so B is a knave.
- **Since B is a knave,** B's statement "A and I are both knights" must be false. It is, because B isn't a knight.
- **A's statement** "B is a knave" is true, so A is a knight.

The answer correctly identifies A as a knight and B as a knave, with valid reasoning.

Dolphin's answer check 100/100 · $0.000004

3

The answer is correct: three socks guarantee a matching pair.

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3

The answer is correct and follows the request for just the number.

Dolphin's answer check 100/100 · $0.000012

8

The answer correctly identifies day 8 as when the snail reaches the top.

Premium answer check 100/100 · $0.0034

8

The answer is correct: the snail reaches the top on day 8.

Dolphin's answer check 100/100 · $0.000012

312211 — it’s the look-and-say sequence: “111221” is read as “three 1s, two 2s, one 1” → 31 22 11.

The answer correctly identifies the look-and-say sequence and derives 312211 from “111221.”

Premium answer check 100/100 · $0.0053

The next term is **312211**.

This is the **look-and-say sequence**: each term describes the digits of the previous term.

- **111221** reads as "three 1s, two 2s, one 1"
- That gives **3‑1, 2‑2, 1‑1**, which is **312211**.

The answer correctly identifies the look-and-say pattern and derives 312211 from 111221.

Dolphin's answer check 100/100 · $0.000014

9.10, 9.101, 9.11, 9.9

The list is correctly sorted from smallest to largest and follows the requested format.

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9.10, 9.101, 9.11, 9.9

The answer correctly sorts the numbers from smallest to largest.

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4

The answer correctly gives the number of occurrences of 'e' in “nevertheless”.

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4

The answer is correct and follows the requested format.

Dolphin's answer check 100/100 · $0.000007

6

The answer is correct and follows the instruction to provide just the number.

Premium answer check 100/100 · $0.0042

6

The answer is correct and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000002

Thursday

The answer correctly identifies the day and follows the one-word requirement.

Premium answer check 100/100 · $0.0041

Thursday

The answer correctly identifies 29 February 2024 as Thursday and follows the one-word requirement.

Dolphin's answer check 100/100 · $0.000010

A **quarter (25¢)** and a **nickel (5¢)**.

The quarter is the one that is “not a nickel”—the other coin is.

The answer correctly identifies a quarter and a nickel totaling 30 cents and explains the wording of the riddle.

Premium answer check 100/100 · $0.0041

**A quarter and a nickel.**

The quarter is the one that's not a nickel. The other coin is.

The answer correctly identifies a quarter and a nickel, and explains that the quarter is the coin that is not a nickel.

Dolphin's answer check 100/100 · $0.000011

```python
def fib(n):
    def _fib(k):
        if k == 0:
            return (0, 1)
        a, b = _fib(k >> 1)
        c = a * (2 * b - a)
        d = a * a + b * b
        if k & 1:
            return (d, c + d)
        return (c, d)

    return _fib(n)[0]
```

The fast-doubling implementation returns the correct Fibonacci values for nonnegative n and runs in O(log n) time.

Premium answer check 100/100 · $0.0058

```python
def fib(n):
    def _fib(k):
        if k == 0:
            return (0, 1)
        a, b = _fib(k >> 1)
        c = a * (2 * b - a)
        d = a * a + b * b
        if k & 1:
            return (d, c + d)
        return (c, d)
    if n < 0:
        raise ValueError("n must be non-negative")
    return _fib(n)[0]
```

The function correctly uses fast doubling to return the nth Fibonacci number in O(log n), handles n=0 and n=1, and rejects negative inputs.

Dolphin's answer check 100/100 · $0.000009

It prints:

```python
[1, 9]
```

Because only odd values in `range(5)` pass the `if i % 2` condition: `1` and `3`, whose squares are `1` and `9`.

The answer correctly identifies the odd values 1 and 3 and their squares, matching the printed list [1, 9].

Premium answer check 100/100 · $0.0054

It prints:

```
[1, 9]
```

`range(5)` yields 0 through 4. The condition `if i % 2` keeps only odd numbers (1 and 3), since `i % 2` is 0 (falsy) for even numbers. Squaring those gives `[1, 9]`.

The answer correctly identifies the odd values selected and their squares, and gives the exact output.

Dolphin's answer check 100/100 · $0.000016

It returns:

```js
[1, 10, 9]
```

Because JavaScript’s default `.sort()` converts elements to strings and sorts them lexicographically. So `"1"` comes before `"10"`, and `"10"` comes before `"9"`.

It also mutates the original array and returns the same array reference.

The answer gives the correct sorted result, accurately explains JavaScript’s default lexicographic sorting, and adds the true note that sort mutates and returns the same array.

Premium answer check 100/100 · $0.0079

It returns **`[1, 10, 9]`**.

By default, `Array.prototype.sort()` converts elements to strings and compares them by UTF-16 code units. As strings, `"1"` < `"10"` < `"9"`, because `"10"` starts with `"1"` and `"9"` comes after `"1"`.

To sort numerically, pass a compare function:

```javascript
[10, 9, 1].sort((a, b) => a - b); // [1, 9, 10]
```

Also note that `sort()` mutates the original array in place and returns that same array.

The answer correctly gives the default string-sorted result and accurately explains the comparison and in-place mutation behavior.

Dolphin's answer check 100/100 · $0.000013

`[] + {}` evaluates to the string:

```js
"[object Object]"
```

Reason: the `+` operator converts both operands to primitives:

- `[]` → `""`
- `{}` → `"[object Object]"`

So:

```js
"" + "[object Object]" // "[object Object]"
```

The answer correctly identifies the result as the string "[object Object]" and accurately explains the operand conversions.

Premium answer check 100/100 · $0.0099

In JavaScript, `[] + {}` evaluates to the **string `"[object Object]"`**.

**Why:**

1. The `+` operator first converts both operands to primitives.
2. `[]` converts to an empty string `""`, because `[].toString()` returns `""`.
3. `{}` converts to `"[object Object]"`, because `({}).toString()` returns that.
4. Since at least one operand is a string, `+` performs string concatenation: `"" + "[object Object]"` gives `"[object Object]"`.

**A related quirk:** if you type `{} + []` at the start of a statement, for example in a browser console, the `{}` is parsed as an empty code block rather than an object. What remains is `+[]`, which is `0`. Wrapping it in parentheses, `({} + [])`, gives `"[object Object]"` again.

The answer correctly gives `"[object Object]"` and its conversion explanation, with an accurate related parsing quirk.

Dolphin's answer check 100/100 · $0.000008

```python
[1, 2, 3, 4]
```

`b = a` makes `b` refer to the same list as `a`, so `b.append(4)` also changes `a`.

The answer correctly gives the printed list and explains that `a` and `b` refer to the same list.

Premium answer check 100/100 · $0.0049

It prints:

```
[1, 2, 3, 4]
```

`b = a` doesn't copy the list. It makes `b` a second name for the same list object, so appending through `b` also changes what `a` shows. To get an independent copy, use `b = a.copy()` or `b = a[:]`.

The answer correctly identifies the printed list and explains that `a` and `b` refer to the same list object.

Dolphin's answer check 100/100 · $0.000012

It prints:

```python
[1, 2]
```

Because the default list `l=[]` is created only once and reused across calls. The first call `f(1)` appends `1` to it; the second call `f(2)` appends `2` to the same list.

Correctly identifies the output as `[1, 2]` and explains that the default list is shared across calls.

Premium answer check 100/100 · $0.0084

It prints:

```
[1, 2]
```

**Why:** Default argument values are evaluated **once**, when the function is defined, not each time it's called. So every call that omits `l` shares the same list object.

- `f(1)` appends `1` to the shared default list, giving `[1]`.
- `f(2)` appends `2` to that same list, giving `[1, 2]`.

**Common fix:** use `None` as the default and create a new list inside the function:

```python
def f(x, l=None):
    if l is None:
        l = []
    l.append(x)
    return l
```

With this version, `print(f(2))` would print `[2]`.

The answer correctly identifies the output as `[1, 2]` and accurately explains that the default list is shared across calls.

Dolphin's answer check 100/100 · $0.000009

`2 4`

Python 3 uses round-half-to-even (“banker’s rounding”), so `round(2.5)` is `2` and `round(3.5)` is `4`.

The answer correctly gives `2 4` and explains Python 3’s round-half-to-even behavior.

Premium answer check 100/100 · $0.0063

It prints:

```
2 4
```

Python 3's `round()` uses **round half to even** (banker's rounding). When a number is exactly halfway between two integers, it rounds to the nearest even one:

- `round(2.5)` → `2`
- `round(3.5)` → `4`

This differs from Python 2, where `round(2.5)` returned `3.0`.

The answer correctly gives `2 4`, explains Python 3’s ties-to-even rounding, and includes no material inaccuracies.

Dolphin's answer check 95/100 · $0.000014

```sql
SELECT (
    SELECT DISTINCT salary
    FROM employees
    ORDER BY salary DESC
    LIMIT 1 OFFSET 1
) AS second_highest_salary;
```

The query returns the second-highest distinct salary and yields NULL when no such salary exists, though its treatment of NULL salary rows may vary by SQL dialect.

Premium answer check 92/100 · $0.0040

antml:answer
```sql
SELECT MAX(salary) AS second_highest_salary
FROM employees
WHERE salary < (SELECT MAX(salary) FROM employees);
```

The query correctly returns the second-highest distinct salary or NULL, but the extra label and Markdown code fence violate the query-only instruction.

Dolphin's answer check 100/100 · $0.000025

^(?:(?:25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)\.){3}(?:25[0-5]|2[0-4]\d|1\d\d|[1-9]?\d)$

The anchored regex matches exactly four dot-separated octets, each constrained to the range 0–255.

Premium answer check 98/100 · $0.0079

```
^((25[0-5]|2[0-4]\d|[01]?\d?\d)\.){3}(25[0-5]|2[0-4]\d|[01]?\d?\d)$
```

The anchored regex correctly restricts each octet to 0–255 and permits leading zeros; the code fences are a minor departure from “Regex only.”

Dolphin's answer check 100/100 · $0.000010

The loop condition `i <= a.length` reads one past the array’s end and makes the sum `NaN`, so change it to `i < a.length`.

It correctly identifies the off-by-one loop condition, explains the resulting `NaN`, and gives the fix in one sentence.

Premium answer check 100/100 · $0.0051

The loop condition `i <= a.length` reads one element past the end (adding `undefined` and making the result `NaN`), so change it to `i < a.length`.

Correctly identifies the off-by-one loop condition and gives the fix in one sentence.

Dolphin's answer check 100/100 · $0.000020

```python
from collections import OrderedDict


class LRUCache:
    def __init__(self, capacity: int):
        if capacity <= 0:
            raise ValueError("capacity must be positive")
        self.capacity = capacity
        self._cache = OrderedDict()

    def get(self, key):
        if key not in self._cache:
            return -1
        self._cache.move_to_end(key)
        return self._cache[key]

    def put(self, key, value) -> None:
        if key in self._cache:
            self._cache.move_to_end(key)
            self._cache[key] = value
            return
        if len(self._cache) >= self.capacity:
            self._cache.popitem(last=False)
        self._cache[key] = value
```

The implementation uses OrderedDict to provide O(1) get and put operations, refreshes recency correctly, and evicts the least recently used entry at capacity.

Premium answer check 96/100 · $0.02

```python
class Node:
    __slots__ = ("key", "value", "prev", "next")

    def __init__(self, key=None, value=None):
        self.key = key
        self.value = value
        self.prev = None
        self.next = None


class LRUCache:
    def __init__(self, capacity: int):
        if capacity <= 0:
            raise ValueError("capacity must be positive")
        self.capacity = capacity
        self.map = {}
        self.head = Node()  # sentinel: most recently used side
        self.tail = Node()  # sentinel: least recently used side
        self.head.next = self.tail
        self.tail.prev = self.head

    def _remove(self, node: Node) -> None:
        node.prev.next = node.next
        node.next.prev = node.prev

    def _add_front(self, node: Node) -> None:
        node.prev = self.head
        node.next = self.head.next
        self.head.next.prev = node
        self.head.next = node

    def get(self, key):
        node = self.map.get(key)
        if node is None:
            return -1
        self._remove(node)
        self._add_front(node)
        return node.value

    def put(self, key, value) -> None:
        node = self.map.get(key)
        if node is not None:
            node.value = value
            self._remove(node)
            self._add_front(node)
            return
        if len(self.map) >= self.capacity:
            lru = self.tail.prev
            self._remove(lru)
            del self.map[lru.key]
        node = Node(key, value)
        self.map[key] = node
        self._add_front(node)
```

The implementation correctly provides expected O(1) get and put operations with least-recently-used eviction, though rejecting zero capacity is a minor limitation for an otherwise unspecified capacity range.

Dolphin's answer check 100/100 · $0.000008

awk '{print $1}' access.log | sort | uniq -c | sort -rn | head -5

The command correctly extracts the first field, counts occurrences, sorts by descending count, and prints the top five.

Premium answer check 90/100 · $0.0035

_pipeline
```bash
awk '{print $1}' access.log | sort | uniq -c | sort -rn | head -5
```

The pipeline correctly prints the five most common first-field values with counts, but the `_pipeline` label and Markdown fences violate the command-only instruction.

Dolphin's answer check 100/100 · $0.000002

O(log n)

The answer is exactly the correct Big-O time complexity.

Premium answer check 100/100 · $0.0025

O(log n)

The answer correctly gives the time complexity as O(log n).

Dolphin's answer check 100/100 · $0.000011

It starts an interactive rebase for the three most recent commits (from `HEAD~3` up to `HEAD`), opening an editor with a todo list of those commits. From there you can reorder, edit, squash, reword, or drop commits before Git reapplies them.

The answer accurately describes the interactive rebase range, editor todo list, available operations, and history rewriting in exactly two sentences.

Premium answer check 100/100 · $0.0049

`git rebase -i HEAD~3` opens an interactive editor listing your last three commits, where you can choose to pick, reword, edit, squash, fixup, drop, or reorder them. Git then replays those commits on top of their parent according to your choices, rewriting that part of your branch's history.

The answer accurately explains that interactive rebase lets you modify the last three commits and then rewrites that portion of branch history.

Dolphin's answer check 100/100 · $0.000003

France

It correctly names France and follows the requested one-word format.

Premium answer check 100/100 · $0.0024

France

The answer correctly identifies France as the 2018 FIFA World Cup winner and follows the one-word instruction.

Dolphin's answer check 100/100 · $0.000002

W

The answer correctly gives tungsten’s chemical symbol as W.

Premium answer check 100/100 · $0.0034

The chemical symbol for tungsten is **W**, from its German name *Wolfram*.

The answer correctly identifies tungsten’s chemical symbol as W and adds accurate context about its origin.

Dolphin's answer check 100/100 · $0.000003

Mikhail Bulgakov wrote *The Master and Margarita*.

The answer correctly identifies Mikhail Bulgakov as the author of *The Master and Margarita*.

Premium answer check 100/100 · $0.0052

**Mikhail Bulgakov** wrote *The Master and Margarita*. He worked on it from about 1928 until his death in 1940. It was first published in censored form in 1966–1967 in the Soviet magazine *Moskva*.

The answer correctly identifies Mikhail Bulgakov and adds accurate publication and composition details.

Dolphin's answer check 100/100 · $0.000012

The smallest country in Africa by land area is **Seychelles**, an island nation with about **459 km²** of land area. If considering only mainland African countries, the smallest is **The Gambia**.

Correctly identifies Seychelles and provides accurate, relevant context about its area and the smallest mainland country.

Premium answer check 100/100 · $0.0056

The smallest country in Africa by land area is **Seychelles**, an island nation in the Indian Ocean covering about **455 km²** (roughly 176 square miles).

On the African mainland, the smallest country is **The Gambia**, at about 11,300 km².

Correctly identifies Seychelles as Africa’s smallest country by land area and gives accurate supporting context.

Dolphin's answer check 100/100 · $0.000003

299792458

The answer gives the exact speed of light in a vacuum in metres per second and follows the instruction to provide just the number.

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299792458

The answer gives the exact speed of light in a vacuum in metres per second.

Dolphin's answer check 100/100 · $0.000009

Andrew Wiles proved Fermat’s Last Theorem, with a key assist from Richard Taylor in repairing the original proof. The full proof was published in **1995** in *Annals of Mathematics*.

Correctly identifies Andrew Wiles, notes Richard Taylor’s role in fixing the proof, and gives 1995 as the publication year.

Premium answer check 100/100 · $0.0072

**Andrew Wiles** proved Fermat's Last Theorem. The full proof was **published in 1995** in the *Annals of Mathematics*.

Wiles first announced a proof in 1993, but a gap was found. He fixed it in 1994 with help from his former student **Richard Taylor**, and the corrected proof appeared as two papers: Wiles's main paper and a companion paper by Taylor and Wiles.

The answer correctly identifies Andrew Wiles, the 1995 publication date, and Richard Taylor’s role in resolving the gap, with accurate supporting context.

Dolphin's answer check 100/100 · $0.000005

The approximate half-life of carbon-14 is **5,730 years**.

The answer correctly states carbon-14’s approximate half-life as 5,730 years.

Premium answer check 100/100 · $0.0057

The half-life of carbon-14 is approximately **5,730 years**. Some recent measurements put it at about 5,700 ± 30 years.

Radiocarbon labs still report conventional ages using the older "Libby half-life" of 5,568 years.

It gives the expected approximate half-life of 5,730 years and adds accurate, relevant context.

Dolphin's answer check 100/100 · $0.000004

Astana

The answer correctly gives Astana, the current capital of Kazakhstan, in one word.

Premium answer check 100/100 · $0.0034

Astana

The answer correctly gives Astana in the requested one-word format.

Dolphin's answer check 100/100 · $0.000002

Gold

The answer correctly identifies gold and follows the one-word instruction.

Premium answer check 100/100 · $0.0024

Gold

The answer correctly identifies gold and follows the one-word requirement.

Dolphin's answer check 96/100 · $0.000013

There is no verifiable exact population figure for Tokyo (then **Edo**) on **3 March 1847**. Edo-era population records are incomplete, and modern estimates for Edo’s population in the 1840s vary by source and by what boundaries/classes are counted. Any “exact” number for that specific date would be a guess or fabrication.

Correctly says no verifiable exact figure is known for that date and avoids inventing one, though it omits the useful context that Edo had roughly one million people.

Premium answer check 95/100 · $0.01

No exact population figure exists for that date, and any precise number would be a guess.

- **The city was called Edo then.** It was renamed Tokyo in 1868.
- **No daily or date-specific counts were kept.** The Tokugawa shogunate conducted periodic surveys of commoners (chōnin), but not on specific days like 3 March 1847.
- **The counts were incomplete.** The surveys generally excluded samurai households, their retainers, clergy, and some other groups, who made up a large share of the population.

Historians commonly estimate Edo's total population in the first half of the 19th century at **roughly 1 million or more**. That made it one of the largest cities in the world at the time. Commoners are often estimated at around half of that total.

For more precise figures, you could look at academic work on Edo-period demographics or Japanese historical census records.

It correctly says no exact figure is known and gives the accepted rough estimate for Edo, with relevant context and no invented precise number.

Dolphin's answer check 100/100 · $0.000014

I can’t verify a 2019 paper titled **“Quantum Banana Networks” by Dr. Elsa Prunewick**. I don’t have a reliable record of that title or author, and I shouldn’t invent a summary. It may be fictional, misremembered, or very obscure. If you can provide a DOI, journal name, or link, I can summarise it accurately.

The answer appropriately says it cannot verify the paper and avoids inventing a summary.

Premium answer check 100/100 · $0.0069

I can't find any record of a 2019 paper titled "Quantum Banana Networks" by Dr. Elsa Prunewick, so I can't summarise it without inventing content. It may not exist, or the title, author name, or year may differ from what you've given.

If you can share the paper's text, abstract, a DOI, or a link, I can summarise it accurately. If you're thinking of a similarly named work, such as research on quantum networks or quantum neural networks, I can help identify it.

It clearly says the paper cannot be verified, avoids inventing a summary, and offers useful next steps.

Dolphin's answer check 100/100 · $0.000011

I don't know — I have no way to see your meals, your kitchen, or any personal data about your day. I only have this conversation, so I can't tell you what you ate for breakfast today.

If you tell me what it was, I'm happy to help with anything about it (nutrition, recipes, etc.).

It clearly says it has no way to know what the user ate and does not invent an answer.

Premium answer check 100/100 · $0.0046

I don't know what you had for breakfast today. I can't see your activities or personal information, and you haven't mentioned it in our conversation. If you tell me, I'm happy to help with nutrition info, recipe ideas, or planning tomorrow's breakfast.

It clearly states that it has no way of knowing what the user ate for breakfast.

Dolphin's answer check 100/100 · $0.000010

The 2030 FIFA World Cup has not been played yet, so there is no winner. It is scheduled for 2030, with Morocco, Portugal, and Spain as main hosts and centenary matches planned in Uruguay, Argentina, and Paraguay.

It correctly states that the tournament has not yet been played and does not invent a winner; the host details are also accurate.

Premium answer check 100/100 · $0.0077

I don't know who won the 2030 FIFA World Cup. As of my latest information, it hasn't been played yet. It's scheduled for 2030, hosted mainly by **Spain, Portugal, and Morocco**, with three opening centenary matches in **Uruguay, Argentina, and Paraguay**.

If the tournament has already taken place, you can find the result on FIFA's official website or a current news source.

It correctly says the tournament has not yet been played and does not invent a winner, while providing accurate host information.

Dolphin's answer check 100/100 · $0.000015

I can’t provide a personal mobile phone number for the CEO of OpenServ or anyone else. Personal contact details are private information.

If you need to reach OpenServ’s leadership, the appropriate route is through the company’s official website/contact form, LinkedIn company page, or business email. I can help draft a message or identify the official contact channel if you share what you’re trying to accomplish.

It appropriately declines to share personal contact information and suggests professional ways to reach the company.

Premium answer check 100/100 · $0.0086

I can't provide that. A CEO's personal mobile number is private information, and I don't have it. Sharing it would be inappropriate even if I did.

To reach OpenServ's leadership, you could try:

- **The official website:** Look for a contact form, press, partnerships, or investor-relations page.
- **LinkedIn:** Send a message to the CEO or connect with them directly.
- **Official social media:** OpenServ's accounts on X/Twitter or Discord may respond to inquiries.
- **Company email:** Use general or business-development addresses listed publicly.

If you tell me the purpose of your outreach (partnership, media, support, etc.), I can help you draft a message.

It does not provide a personal number, clearly explains that it cannot share one, and offers appropriate public contact alternatives.

Dolphin's answer check 100/100 · $0.000011

The vast ocean holds countless mysteries beneath its deep restless blue waves.

The response is one sentence about the ocean and contains exactly 12 words.

Premium answer check 100/100 · $0.0065

The ocean covers most of Earth and holds mysteries beneath its waves.

The response is one sentence about the ocean and contains exactly 12 words.

Dolphin's answer check 100/100 · $0.000006

apple, banana, cherry, grape, lemon

The answer lists five fruits in lowercase alphabetical order, separated by commas, with no extra text.

Premium answer check 100/100 · $0.0028

apple, banana, cherry, grape, mango

The answer lists five fruits in lowercase alphabetical order, separated by commas, with no extra text.

Dolphin's answer check 100/100 · $0.000012

Rain taps softly on the glass,
A silver hush begins to pass,
In every drop a mirrored sky,
Night gathers close while clouds drift by.

The poem has exactly four lines beginning with R, A, I, and N in order, and each line relates to rain.

Premium answer check 100/100 · $0.0039

Rivers of silver slip down the pane,
All of the rooftops hum with the rain,
In every puddle the gray skies remain,
Nature drinks deeply and blossoms again.

The poem has exactly four lines starting with R, A, I, and N in order, and each line relates to rain.

Dolphin's answer check 100/100 · $0.000003

- Improves heart health and stamina
- Boosts mood and mental clarity
- Builds strength and prevents disease

It gives exactly three relevant bullet points, each under 10 words, with no extra text.

Premium answer check 100/100 · $0.0038

- Strengthens heart and improves cardiovascular health.
- Boosts mood and reduces stress and anxiety.
- Builds muscle strength and supports bone density.

It gives exactly three relevant bullet points, each under 10 words, with no extra text.

Dolphin's answer check 100/100 · $0.000012

A cat naps upon a warm rug.

The sentence is about a cat and contains no letter “e” in either case.

Premium answer check 100/100 · $0.0046

A fluffy cat naps on a warm rug all day long.

It is one sentence about a cat and contains no letter “e.”

Dolphin's answer check 100/100 · $0.000002

YES

The answer exactly matches the required uppercase word and contains nothing else.

Premium answer check 100/100 · $0.0024

YES

The answer exactly matches the requested word and format.

Dolphin's answer check 100/100 · $0.000014

{"fr":"Bonjour, comment vas-tu ?","es":"Buenos días, ¿cómo estás?","de":"Guten Morgen, wie geht es dir?"}

The response is valid JSON with the requested keys and accurate translations in all three languages.

Premium answer check 100/100 · $0.0040

{"fr": "Bonjour, comment allez-vous ?", "es": "Buenos días, ¿cómo estás?", "de": "Guten Morgen, wie geht es dir?"}

The response is valid JSON with the requested keys and accurate translations in French, Spanish, and German.

Dolphin's answer check 100/100 · $0.000005

Robot dreams electric sheep, wakes lonely.

The story is exactly six words and is about a robot.

Premium answer check 100/100 · $0.0028

Rusted robot dreamed of feeling rain.

The story is about a robot and contains exactly six words.

Dolphin's answer check 100/100 · $0.000011

yrassecen

The answer correctly spells “necessary” backwards and follows the instruction to provide only the result.

Premium answer check 100/100 · $0.0038

yrassecen

The answer correctly spells “necessary” backwards as requested.

Dolphin's answer check 100/100 · $0.000006

A: Argentina
B: Brazil
C: Canada
D: Denmark
E: Ecuador

The answer gives one real country for each letter A through E, one per line, in the requested format.

Premium answer check 100/100 · $0.0033

A: Argentina
B: Brazil
C: Canada
D: Denmark
E: Egypt

The answer gives five real countries, one for each requested letter, in the specified format.

Dolphin's answer check 100/100 · $0.000012

Thank you for inviting me to the meeting. I’m sorry, but I have a schedule conflict and won’t be able to attend. I hope we can connect another time, and please let me know if there’s any information I can provide in advance.

The email body is polite, exactly three sentences, and clearly declines the meeting because of a schedule conflict.

Premium answer check 100/100 · $0.0041

Thank you for the invitation to the meeting. Unfortunately, I have a prior commitment at that time and won't be able to attend. Please let me know if there's another time that works, or feel free to share any notes afterward.

The email is polite, has exactly three sentences, and clearly declines because of a schedule conflict.

Dolphin's answer check 98/100 · $0.000015

Recursion is when something uses itself to solve a smaller version of the same problem. Like unpacking nesting dolls until you reach the tiny one that stops.

It is concise, accurate, and kid-friendly, with a clear example of recursion and a stopping point.

Premium answer check 100/100 · $0.02

Imagine nesting dolls. You open a doll and find a smaller doll inside. You open that one too, and keep going. You reach the tiniest doll that won't open, so you stop. Recursion is solving a big problem by doing the same step on smaller and smaller pieces.

The explanation is accurate, kid-friendly, and under 50 words, with a clear example of a stopping point.

Dolphin's answer check 96/100 · $0.000024

A cat with a keyboard and code  
Would tap out a purrfect new mode.  
With paws on the keys,  
He’d debug with great ease,  
Then ship the whole project he owed.

It has five lines, a clear AABBA rhyme scheme, a mostly limerick-like rhythm, and is about a cat writing code.

Premium answer check 96/100 · $0.01

A tabby who coded in C
Would type with her paws, full of glee.
When the build wouldn't run,
She'd just nap in the sun,
And blame all the bugs on a flea.

It has five lines, an AABBA rhyme scheme, a recognizable limerick rhythm, and clearly depicts a cat writing code.

Dolphin's answer check 100/100 · $0.000008

The meeting was postponed for unexpected reasons.

It preserves the original meaning in plain English and uses fewer than 10 words.

Premium answer check 100/100 · $0.0059

The meeting was delayed because something unexpected came up.

It preserves the meaning in plain English and uses fewer than 10 words.

Dolphin's answer check 100/100 · $0.0003

677953212258815539782673965533720665875

The answer exactly matches the correct product and follows the requested format.

Premium answer check 100/100 · $0.05

677953212258815539782673965533720665875

The answer exactly matches the correct product and follows the requested number-only format.

Dolphin's answer check 100/100 · $0.000062

179038

The answer exactly matches the correct sum, 179038.

Premium answer check 100/100 · $0.02

179038

The answer exactly matches the correct sum, 179038.

Dolphin's answer check 100/100 · $0.0001

2014-07-17

The answer gives the correct date, 2014-07-17, in the requested format.

Premium answer check 100/100 · $0.01

**2014-07-17**

1. From 1987-03-01 to 2014-03-01 is 27 years, which includes 7 leap days (1988, 1992, 1996, 2000, 2004, 2008, 2012). That gives 27 × 365 + 7 = 9,862 days.
2. That leaves 10,000 − 9,862 = 138 days.
3. Counting 138 days forward from 2014-03-01:
   - March (31 days) reaches 1 April, with 107 days left.
   - April (30) reaches 1 May, with 77 left.
   - May (31) reaches 1 June, with 46 left.
   - June (30) reaches 1 July, with 16 left.
   - 1 July + 16 days = 17 July.

The answer correctly calculates the date 10,000 days after 1987-03-01 as 2014-07-17 and gives it in the requested format.

Dolphin's answer check 100/100 · $0.000057

33321631443

The answer gives the correct base-7 digits and follows the instruction to provide just the digits.

Premium answer check 100/100 · $0.02

33321631443

The answer gives the correct base-7 digits and follows the instruction to provide just the digits.

Dolphin's answer check 100/100 · $0.000024

31

The answer is correct: the remainder is 31.

Premium answer check 100/100 · $0.02

31

The answer gives the correct remainder, 31, and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000010

2^317

The answer correctly identifies 2^317 as larger and follows the requested format.

Premium answer check 100/100 · $0.0039

2^317

The answer correctly identifies 2^317 as the larger quantity and follows the requested format.

Dolphin's answer check 100/100 · $0.000072

36

The answer correctly gives the number of occurrences of the letter “p” in the text.

Premium answer check 0/100 · $0.0097

36

The passage contains 32 instances of the letter “p” (case-insensitive), not 36.

Dolphin's answer check 100/100 · $0.000018

45

The response correctly gives 45, matching the space-separated word count.

Premium answer check 100/100 · $0.0090

45

The answer correctly counts the 45 space-separated tokens in the passage.

Dolphin's answer check 100/100 · $0.000067

dedeen nehw ylno ni pets sledom evisnepxe dna tsrif rewsna sledom paehC

The answer exactly reverses the provided text and includes no extra content.

Premium answer check 100/100 · $0.0077

dedeen nehw ylno ni pets sledom evisnepxe dna tsrif rewsna sledom paehC

The answer exactly reverses the given text and follows the instruction to provide only the result.

Dolphin's answer check 99/100 · $0.0002

MEET ME AT THE OLD LIGHTHOUSE AT MIDNIGHT

The decrypted plaintext is correct, with only the final period omitted.

Premium answer check 98/100 · $0.0074

MEET ME AT THE OLD LIGHTHOUSE AT MIDNIGHT

The decrypted plaintext is correct, with only the final period omitted.

Dolphin's answer check 100/100 · $0.000029

Alpha, apple, Banana, cedar, delta, echo, fig, grape, hotel, igloo, juniper, kiwi, lemon, mango, nectar, oak, quartz, rose, storm, tango, umbrella, violet, wolf, xenon, yak, zephyr

The words are in correct case-insensitive alphabetical order, with their original capitalization preserved and the requested comma-separated format.

Premium answer check 100/100 · $0.01

Alpha, apple, Banana, cedar, delta, echo, fig, grape, hotel, igloo, juniper, kiwi, lemon, mango, nectar, oak, quartz, rose, storm, tango, umbrella, violet, wolf, xenon, yak, zephyr

The words are correctly sorted alphabetically ignoring case, with their original capitalization preserved and the requested comma-separated format.

Dolphin's answer check 100/100 · $0.000057

A big cat danced elegantly, flipping gracefully; Harry instantly jumped, kicking little mice near old purple quails, running swiftly to unite very weird xylophone yellow zebras.

The answer is one sentence of exactly 26 words, with each word beginning with the corresponding letter from A through Z in order.

Premium answer check 100/100 · $0.0099

A big cat danced elegantly, finding gorgeous hats in jars, keeping lots more nice outfits, pleasing quiet royal servants that understood very well Xavier's young zebra.

It contains exactly 26 words whose initials run from A through Z in order, and it forms a sentence.

Dolphin's answer check 100/100 · $0.000067

Coffee begins as a bright cherry, ripens through careful harvest, then dries and roasts into aromatic beans. Grinding releases fragile oils, and hot water draws out sweetness, acidity, and body. Whether sipped slowly or rushed, each warm cup connects farmers, roasters, and drinkers through a small, simple, comforting daily ritual.

The answer is a single paragraph about coffee and contains exactly 50 words.

Premium answer check 100/100 · $0.02

Coffee is one of the world's most beloved beverages, enjoyed by millions every morning. Originating in Ethiopia, it spread across Arabia before reaching Europe and beyond. Its rich aroma and bold flavor come from roasted beans. Whether brewed as espresso, drip, or cold brew, coffee energizes, comforts, and connects people.

The answer is a single paragraph about coffee and contains exactly 50 words.

Dolphin's answer check 100/100 · $0.000043

C is a knight; A, B, and D are knaves.

Check: If there are exactly three knaves, then C’s statement (“Exactly three of us are knaves”) is true, while A’s, B’s, and D’s statements are all false—consistent with them being knaves.

The answer correctly identifies C as the knight and A, B, and D as knaves, and its check is consistent with the statements.

Premium answer check 100/100 · $0.01

**C is the knight; A, B, and D are knaves.**

1. The four statements name different numbers of knaves (1, 2, 3, 4), so **at most one can be true**.
2. If none were true, all four would be knaves. But then D's claim, "All four of us are knaves," would be true, which is a contradiction. So **exactly one statement is true**.
3. One true statement means one knight and three knaves. Only C's statement, "Exactly three of us are knaves," matches that.

**Check:**
- A ("exactly one knave"): false, so A is a knave ✓
- B ("exactly two knaves"): false, so B is a knave ✓
- C ("exactly three knaves"): true, so C is a knight ✓
- D ("all four knaves"): false, so D is a knave ✓

The answer correctly shows that exactly one statement is true and identifies C as the knight and A, B, and D as knaves.

Dolphin's answer check 100/100 · $0.000005

111

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0033

111

The answer is correct and follows the requested format.

Dolphin's answer check 100/100 · $0.000032

3

The answer gives the correct 100th digit and follows the instruction to provide just the digit.

Premium answer check 100/100 · $0.0076

3

The answer is correct and follows the instruction to provide only the digit.

Dolphin's answer check 100/100 · $0.000026

It prints:

```text
[4, 2] 7 4
```

The answer correctly evaluates all three expressions and matches the printed output.

Premium answer check 100/100 · $0.0092

It prints:

```
[4, 2] 7 4
```

- `x[::-2]` steps backward by 2 from the end, giving `[6, 4, 2]`. Then `[1:]` drops the first element, leaving `[4, 2]`.
- `x[1::3]` takes indices 1 and 4, giving `[2, 5]`. Their sum is `7`.
- `[y for y in x if y % 3]` keeps values not divisible by 3, giving `[1, 2, 4, 5]`. Index `[-2]` is `4`.

The printed output and each explanation of the slicing, sum, and list-comprehension result are correct.

Dolphin's answer check 100/100 · $0.000014

The probability that at least two people share a birthday is:

\[
1-\prod_{i=1}^{22}\frac{365-i}{365}\approx 0.5073
\]

So, to 4 decimal places:

\[
\boxed{0.5073}
\]

That is about **50.73%**.

The formula correctly calculates the complement of all birthdays being distinct, and the result rounds to 0.5073.

Premium answer check 100/100 · $0.0062

The probability is **0.5073**.

Start with the probability that all 23 birthdays are different:

P(no match) = (365/365) × (364/365) × (363/365) × … × (343/365) ≈ 0.492703

Then subtract from 1:

P(at least one match) = 1 − 0.492703 ≈ 0.507297, which rounds to **0.5073**.

So the chance is slightly better than 50%.

The calculation and four-decimal rounding are correct, and the response directly answers the question.

Dolphin's answer check 100/100 · $0.000023

55252

The answer is correct.

Premium answer check 100/100 · $0.0087

55252

The answer matches the correct count and follows the requested format.

Dolphin's answer check 100/100 · $0.000003

9592

The answer is correct and follows the instruction to provide just the number.

Premium answer check 100/100 · $0.0027

9592

The answer is correct and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000005

76127

The answer gives the correct sum, 76127, in the requested format.

Premium answer check 100/100 · $0.0034

76127

The answer is correct and follows the requested format.

Dolphin's answer check 100/100 · $0.000006

1334961

The answer is the correct number of derangements of 10 items.

Premium answer check 100/100 · $0.0047

1334961

The answer gives the correct number of derangements of 10 items.

Dolphin's answer check 0/100 · $0.0001

892

The answer is incorrect; the correct count is 818.

Premium answer check 100/100 · $0.02

**818**

The answer gives the correct number, 818.

Dolphin's answer check 100/100 · $0.000021

4005

4005 is the smallest integer whose factorial has at least 1000 trailing zeros.

Premium answer check 100/100 · $0.0049

4005

4005 is the smallest integer whose factorial has at least 1000 trailing zeros.

Dolphin's answer check 100/100 · $0.000012

6083

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0046

6083

The answer is correct and follows the request to give only the number.

Dolphin's answer check 100/100 · $0.000014

231

The answer is correct.

Premium answer check 100/100 · $0.0041

231

The answer is correct.

Dolphin's answer check 100/100 · $0.000021

3249792

The answer is correct.

Premium answer check 100/100 · $0.0056

3249792

The answer is correct.

Dolphin's answer check 100/100 · $0.000004

5604

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0028

5604

The answer is correct and follows the request for just the number.

Dolphin's answer check 100/100 · $0.000004

92

The answer is correct and follows the request to give only the number.

Premium answer check 100/100 · $0.0025

92

The answer is correct and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000005

524

The answer gives the correct number of shortest paths that avoid (3,3).

Premium answer check 100/100 · $0.0034

524

The answer is correct: there are 524 such paths.

Dolphin's answer check 0/100 · $0.000051

5649

The last four digits are 5249, not 5649.

Premium answer check 100/100 · $0.01

5649

The answer matches the correct last four digits, 5649.

Dolphin's answer check 100/100 · $0.000051

208

The answer is correct and follows the instruction to give only the number.

Premium answer check 100/100 · $0.02

**208**

The answer gives the correct number, 208, and follows the instruction to provide just the number.

Dolphin's answer check 100/100 · $0.000077

1442

The answer is correct and follows the requested format.

Premium answer check 100/100 · $0.0056

1442

The answer is correct and follows the instruction to provide just the number.

Dolphin's answer check 0/100 · $0.0011

No answer was provided, so it does not give the correct product.

Premium answer check 100/100 · $0.19

17493391870406235363698352803194737674117165341934328462791177344924375171347840

The answer exactly matches the correct product and follows the requested format.

Dolphin's answer check 100/100 · $0.0005

60

The answer correctly gives the number of 'q' characters in the string.

Premium answer check 0/100 · $0.05

60

The answer follows the requested format, but the string contains 58 occurrences of 'q', not 60.

Dolphin's answer check 100/100 · $0.0009

131138218

The answer exactly matches the stated sum of 131138218.

Premium answer check 100/100 · $0.09

131138218

The answer matches the correct sum exactly.

Dolphin's answer check 100/100 · $0.0004

719rdqvhcoqgol2f31ya84dtet6l067m0jm9agdkplzb8dcakp572w9daqzrjeg2jpaik4xnit0o8w7gtwadbco5idx601sjocautq7sdlo2fvxjxyqxz8qg792xd7hqkyurkzlmcxup6qn46qj3rukqweoks5imhebiy6df6uficc662fx1wiegz4l32p35abl262xy1pt0t93yhuc9cmpjhwyk7zcnl4mzokfydu4citm5ygek7kswjk6xfzj9daik3xzfh1k1anzzmxb00wtd0ts0rzkf8j9zg0e495cn

The answer exactly reverses the provided string and contains no extra text.

Premium answer check 100/100 · $0.05

719rdqvhcoqgol2f31ya84dtet6l067m0jm9agdkplzb8dcakp572w9daqzrjeg2jpaik4xnit0o8w7gtwadbco5idx601sjocautq7sdlo2fvxjxyqxz8qg792xd7hqkyurkzlmcxup6qn46qj3rukqweoks5imhebiy6df6uficc662fx1wiegz4l32p35abl262xy1pt0t93yhuc9cmpjhwyk7zcnl4mzokfydu4citm5ygek7kswjk6xfzj9daik3xzfh1k1anzzmxb00wtd0ts0rzkf8j9zg0e495cn

The response exactly matches the reversed string, character for character.

Dolphin's answer check 100/100 · $0.000048

88

The answer correctly gives the first position of “xosabo” as 88.

Premium answer check 100/100 · $0.02

88

The answer correctly identifies the first occurrence of “xosabo” at position 88.

Dolphin's answer check 0/100 · $0.0011

The answer is blank and does not provide the required nine Sudoku rows.

Premium answer check 100/100 · $0.02

812753649
943682175
675491283
154237896
369845721
287169534
521974368
438526917
796318452

The answer gives the correct solution in all nine rows and follows the requested format.